JP2010541169A - Document identifier subassembly - Google Patents

Abstract

  A subassembly includes a housing, a light pipe core having an upper diffusing surface, a light control component associated with the upper diffusing surface, and at least one light source coupled to the housing. Preferably, the light control component includes at least one aperture or aperture array and can be formed of, for example, a plastic or polymer material. The aperture can be in the form of an elongated slit, although other shapes are appropriate for some applications. This subassembly can be used in a variety of applications, including use as part of a document identifier.

Description

  The present disclosure relates to a small classifier subassembly that illuminates a document with light at a substantially constant irradiance level even if the distance between the light source and the document varies from document to document.

  In the field of banknote identification, for example, an identification machine used in, for example, a vending machine typically uses an optical sensor, a magnetic sensor, and other sensors to obtain data from an inserted banknote. In some units, a plurality of light emitting diode (LED) light sources and phototransistor receivers are placed on either side of the bill path to generate a signal corresponding to the light transmitted through the bill as the bill moves in its vicinity. . This signal is processed to determine certain information, such as the position of the banknote in the passage and the authenticity of the banknote. This signal is generally compared to a predetermined measurement value stored in memory corresponding to a real bill.

  Conventional banknote recognition systems that utilize LED light sources also use lenses to focus the light to meet system performance requirements. However, some configurations do not provide sufficient optical signal intensity levels to accurately identify the document. Other designs utilize high power light sources and focusing elements and are therefore expensive to manufacture. In addition, the bill passage is generally designed to be large enough to avoid jamming, so sensor readings can be adversely affected. This is because the sensing signal varies depending on the distance of the bill from the light source.

  The present disclosure relates to subassemblies for document identifiers. In this disclosure, the term “document” includes, but is not limited to, banknotes, banknotes, securities, securities documents, money, checks, coupons, bank bills, certificates, and any other similar value. Including.

  The subassembly can include a housing, a light pipe core having an upper diffusing surface, a light control component associated with the upper diffusing surface, and at least one light source coupled to the housing.

  Preferably, the light control component includes at least one opening and can be formed of, for example, a plastic or polymer material. In some implementations, the light control component includes an aperture array. The openings can be in the form of elongated slits, but other shapes may be appropriate for some applications. Other features of light control components included in some implementations are described in more detail below.

  In some implementations, the subassembly includes a prismatic structural layer, such as a brightness enhancement film, between the upper diffusing surface and the light control component. The diffusion surface can include, for example, a random rough structure, a constant pitch pattern structure, or a variable pattern of protrusions. The housing can include one or more input optical ports at one or more ends of the light pipe core. The light source can include, for example, a light housing formed of a reflective material and one or more light emitting diodes (LEDs). For some applications, additional light housings and different wavelength LEDs can be included. The housing can also include first and second reflective shells configured to surround the light pipe core.

  A document sensing arrangement is also disclosed. The document sensing arrangement includes a light source subassembly for placement on a first side of the document path and a light sensor for placement on a second side of the document path opposite the light source subassembly. . The light control component can include the features described above as well as various features discussed in more detail below.

  A method for illuminating a document in a document path with a generally rectangular beam of substantially uniform light using a document identifier subassembly is also described. A prismatic structural layer within the subassembly can be used to increase the light intensity output. This method generates a signal that represents the authenticity or characteristic of the document based on light passing through the document, or a signal that represents the authenticity or characteristic of the document based on light reflected from the surface of the document. It can also include generating.

  A method of making a document identifier subassembly is also disclosed. The method includes fabricating a light pipe core for providing light output across the document path, fabricating a diffusing structure on the output side of the core, and adding a light control component to the diffusing structure. . The light control component can include the features described above as well as various features discussed in more detail below.

  This method can include several implementations of fabrication methods for connecting the reflective housing to the light pipe core. Further, the method can include coupling at least one LED light source package to the housing and can also include adding at least one layer of brightness enhancement film between the diffusing structure and the light control component. .

  In some implementations, fabricating a light pipe core to provide light output across the document path, fabricating a diffusing structure layer, and fabricating a louver structure layer on the output side of the core. Including light bar structure fabrication techniques are provided.

  Some implementations provide one or more of the following advantages. The document identifier subassembly can illuminate the document uniformly across the height and width of the banknote passage, thereby limiting signal variability across the range of inserted document positions and making the identification process more accurate become. The subassembly can illuminate the entire width of the passageway, thereby allowing a full scan of the entire surface of the document, improving the reliability of document recognition. This design allows multiple wavelengths of light to be used with only a few light source components, and the subassembly is ideal for use in document classifiers with limited physical space It has a small size.

  Various aspects of the invention are set forth in the following claims. Various other features and advantages will be readily apparent from the following detailed description and the accompanying drawings.

It is a simplified top view of a document passage. It is a side view of the structure 15 which consists of a single LED light source and a light receiver. It is a simplified expanded sectional view of one composition of a document identification machine. It is a disassembled perspective view of a document identification machine subassembly. It is a figure which shows an example of a document identification machine subassembly. It is a figure which shows an example of a light control component. FIG. 6 shows further details of a light control component according to a particular example. It is a perspective view of a subassembly. FIG. 3 is an enlarged simplified cross-sectional schematic view of a light pipe core. It is a figure which shows an example of the dimension of the light pipe core suitable for using with a banknote identification machine subassembly. It is a figure which shows what expanded the part C of FIG. 6B. It is an expansion simplification side surface schematic diagram showing the prism structure of a brightness improvement film. FIG. 2 is an enlarged simplified exploded perspective schematic view of an optical core assembly for a document identifier. FIG. 2 is an enlarged simplified exploded perspective schematic view of an optical core assembly for a document identifier. Geometric mapping.

  FIG. 1 is a simplified top view of a document path 5 having a light spot configuration 2 comprised of a plurality of light spots 3 arranged in a single line so as to cover the width 4 of the document path 5. The width 4 is shown as a banknote or bill 6 wider than the widest document of the set of documents to be sampled and narrower than the document path. In this example, the document 6 is slightly inclined when moving in the direction of the arrow 7.

  Although the subassembly is described herein with respect to its use in a document identifier, it can also be used in other devices.

  Referring again to FIG. 1, the spot 3 can be generated by one or more light sources, typically one or more light emitting diodes (LEDs). With such a configuration, when the inserted banknote 6 moves in the direction of the arrow 7 in the banknote passage, almost 100% of the inserted banknote 6 can be scanned. Specifically, the bill can be transferred between one or more light sources and one or more light receiving sensors (not shown) disposed on the opposite side of the passage. In such a configuration, the signal generated by the light receiver, corresponding to the light transmitted through the banknote, is the length and width of the banknote, banknote position at any particular moment, banknote authenticity, banknote characteristics, and It can be processed to determine information such as the billing country. In order to receive the light reflected from the banknote in the same manner as described for the transmitted light, the light receiver can be arranged on the same side as the light source.

  In some implementations, there are 10-12 light spots across the bill path to sample data from the bill, but more or fewer spots could be used. Each spot can be, for example, about 7.6 mm in diameter, and each spot is sampled at three or more wavelengths. For example, light spots having wavelengths in the visible, infrared, and near-infrared spectra can be used and the resulting data can be processed to collect various types of information from banknotes. . Signal processing techniques for determining banknote characteristics, authenticity, nationality, face value, and / or banknote position within the passage are beyond the scope of this disclosure and will not be discussed in detail herein.

  FIG. 2 is a side view of the configuration 15 composed of a single LED light source and light receiver, in which the light source 16 and the light receiver 20 are on both sides of the bill passage 5. The LED light source 16 is arranged near the focal point of the focusing lens 18 in order to generate a substantially parallel light beam 21 towards the bill 6 through an opening opened in the front wall 17 of the bill passage 5. A part of the banknote interrupts a part of the light beam 21, resulting in a transmitted signal 22 that has passed through the banknote. A detector 20 such as a PIN diode, which can include a focusing lens, is placed at a sufficient distance “d” from the rear wall 19 so that the noise inherent in the light transmitted through the banknote is minimized. The The height “h” of the banknote path can be about 2 mm to 2.5 mm, which is sufficient to minimize the rate at which banknotes are jammed, and the width 4 of the banknote path accommodates banknotes of various widths. Therefore, it can be larger than 90 mm.

  In order to prove the authenticity of the banknote or to simplify the data processing necessary to characterize the banknote, it is desirable to illuminate the banknote substantially uniformly. In practice, due to the size and light transmission characteristics of existing LED light sources, the generation of parallel beams and uniform spots can only be mimicked with a configuration of the type shown in FIG. A group of such sensors arranged in a configuration like that shown in FIG. 1 may be sufficient to determine document position, but the generated signal generates data for determining authenticity. However, it is not completely satisfactory. In addition, if several LED dies are used, the minimum die spacing can cause spot offsets, and therefore tight tolerances must be imposed on the die placement, thereby reducing fabrication costs. Will increase.

  FIG. 3 is a simplified enlarged cross-sectional view of one configuration of the document identification device 30. The document identifier 30 includes a light sensor arrangement 32 on the first side of the document path 5 and a subassembly 40 including a light bar 35 on the second side of the path. In this implementation, two transparent windows 31 and 33, which can be constructed from Lexan ™ material, define a portion of the document path 5 between them. The photosensor configuration 32 includes an array of ten lenses 36 arranged in front of a sensor array 38 consisting of ten detectors mounted on a printed circuit board (PCB) 34. These detectors generate an electrical signal corresponding to the light transmitted through the document as it travels through the passage 5 between the light source and the sensor, and this signal is then transmitted by a microprocessor connected to the PCB 34. It is processed. A suitable detector array can also be placed on the same side of the passage as the light source to generate a signal based on the light reflected from the document. The signals generated by these detectors can be used to determine the validity of the document.

  The light bar 35 of FIG. 3 is attached to the light PCB 37 and provides light that exits in the Z direction from the top surface and illuminates the document at a constant level regardless of the document position within the volume of the document path 5. When a document is transported through the document identifier configuration 30, it may be closer to either the optical sensor configuration 32 or the subassembly 40, depending on the transport conditions and / or the condition or fitness of the document. is there. For example, a particular transport mechanism can transport banknotes (ie, banknotes) through configuration 30 at a constant speed, but the exact position of the banknote within the height “h” of passage 5 is May differ for each banknote. Its position may vary depending on whether a particular banknote is a new banknote that is about to break, or an old, frayed banknote. When used in a document identifier, the light emitted by the light bar 35 covers an area that is at least 70 millimeters (mm) in length (the width of the banknote passage), at least 7 mm in depth, and is about 2.5 mm. Should be uniform throughout height “h”. However, this light pipe core geometry, which includes a long side and a substantially shorter short side, can result in large illumination differences at different heights “h”. With the appropriate light control component (LCC) described in detail below, the geometric limitations of the illumination pattern are overcome and the document remains constant regardless of its position within the height “h” of the passage. It becomes possible to illuminate at the level.

  FIG. 4A is an exploded perspective view of one implementation of the document identifier subassembly 40. Subassembly 40 includes a light pipe core 42 that includes a top surface 44. A first reflective shell 46 and a second reflective shell 48 are configured to surround the light pipe core 42, and a brightness enhancement film (BEF) 50 and a light control component (LCC) 52 are connected to the light pipe core. It is configured so that it can be attached to the upper surface 44 of the core 42. The two reflective shell portions 46, 48 are clipped together around the light pipe core 42 as shown in FIG. 4B, so that there is minimal spacing between the core and the shell.

  The light pipe core 42 can be formed of, for example, a transparent polycarbonate or acrylic material and can be polished to favor all internal reflections except the top surface 44. The first and second reflective shells 46, 48 may be formed of a white grade polybutylene terephthalate (PBT) polymer material. The inner surface can include a reflective material, which can be white and diffusely reflective. A suitable PBT reflective material is available from the Bayer Company under the name “pocan B 7375”, but similar white and diffusive materials such as Spectralon ™ can also be used. The white material allows a suitable nearly flat spectral response to occur, at least over the visible to near infrared wavelength spectral region. The first opening 45 and the second opening 47 at both ends of the protective shell form an input port for a light source (not shown), and the upper surface 44 forms a light output area. In some implementations, the output light area can have a diffuser structure for extracting light from the core. A suitable diffuser structure can be obtained by sanding the surface to obtain a random rough pattern, or molding a rough random structure on the top surface 44. Other diffuser structures can also be used.

  FIG. 5 is a perspective view of a portion of the subassembly 40 shown in FIG. 4B in order to show the arrangement of the first multi-die LED package 54 and the second multi-die LED package 56. Each of the multi-die packages 54 and 56 may include two or more LEDs, and in this implementation, the packages are disposed at both ends of the light pipe core 42 to form a light source. These LEDs may be of different wavelengths or the same wavelength. If different wavelength LEDs are utilized, they may be in the same LED package or in different LED packages. In this configuration, the LEDs are mounted horizontally on the PCB and the light pipe core has a generally trapezoidal shape. However, in some implementations, only one LED light source, for example located at the first opening 45, can be used.

  In the illustrated example, the LCC 52 has a macro array of slits (eg, elongated openings) 100 formed in a single plastic element (see FIG. 4C). Light travels through these openings and is stopped by the wall 102 formed of the remaining material of the LCC element.

  An example of the dimensions of the LCC 52 is shown in FIG. 4D, where the unit of length is millimeters (mm). For example, the thickness of the illustrated LCC 52 is about 1.32 mm. In this example, the LCC has a louver structure with an array of slit-type openings having a width of approximately 1.8 mm. The interval between the slit openings is formed by forming the thickness of the wall portion of the louver structure, and is about 0.64 mm. The length of the slit opening is about 11.5 mm. The dimensions (eg, length, width, and spacing) may vary depending on the requirements of a particular application. Accordingly, different dimensions may be appropriate for other implementations.

  In some implementations, the louver structure 76 consists of an array of circular or other shaped openings. The use of an elongated aperture is advantageous because it limits the exit angle differently in two orthogonal directions: a direction along the slit direction and a direction perpendicular to the slit direction. When a non-linear shape is used, the emission angle is limited in various directions depending on the shape. For example, when the aperture is circular, the exit angle is equally limited in all directions.

  In some implementations, the optical structure of the LCC 52 is optimized based on the desired geometry of the distribution of light exiting the LCC. In particular, the size, numerical aperture, and thickness of the LCC 52, and the arrangement of the openings may be different together or alone to optimize the geometry of the light distribution exiting the LCC 52.

  In some implementations, a continuous slit with the length of the light bar is used. However, in order to improve the rigidity of the LCC 52 and to maintain the spacing between the louver walls 102, it is desirable to segment the length and insert the bridge portion 104 (see FIG. 4C). In the illustrated example, the LCC 52 is configured such that the louver structure is divided into 5 or 6 segment slit-type openings 100 along the length of the LCC 52. Further, in the illustrated example, the louver structure is divided into five segments along the width of the LCC 52. It is desirable to stagger the distribution of slit-type openings 100 over the entire area of the light bar. A linear array of sensors can be arranged to receive the light from the light bar exiting the LCC 52. In some implementations, the bridge portion 104 is located outside the field of view of the detector used to receive the light exiting the LCC 52.

  In some implementations, the LCC 52 is configured with a group of apertures 100 configured to control light exiting the LCC. The LCC 52 can be manufactured using a variety of processes including, but not limited to, injection molding, laser cutting, and stamping. The LCC 52 can be constructed as a stack of thin foil layers each having the same opening configuration. In implementations where the LCC 52 is a molded product, any suitable resin can be used during the manufacturing process. For example, a liquid crystal polymer (LCP) type resin such as Ticona Vectra can be used. Manufacturing LCC 52 using an LCP type resin makes it possible to manufacture the extra thin but rigid walls required for some applications.

  FIG. 6A is an enlarged simplified cross-sectional schematic view of the light pipe core 42 to show how light from the LED light source 54 exits the top surface 44. Specifically, FIG. 6A shows the light from the LED light source 54 entering the light pipe core 42 via the input port 45 (formed by the reflective shell portions 46 and 48 shown in FIG. 4A). The first angled wall 49a is a combination of the walls 46a and 48a, and the second angled wall 49b is a combination of the walls 46b and 48b shown in FIG. 4A. In the implementation of the light pipe core 42 of FIG. 6A, the light is of a ray such as ray 51 having an angle of incidence greater than the critical angle (as defined by the reflectivity of the transparent plastic, which is typically 1.5) In some cases, it is reflected by total internal reflection (TIR) or, in the case of rays such as ray 53, having an angle of incidence less than the critical angle, by reflection of the wall of the mixer shell surrounding the light pipe. . The reflected rays are sent back into the mixing structure and reflected multiple times as shown until the beam reaches the diffuser area on top surface 44 and exits as shown schematically in area 55. be able to. The light from the LED is generally deflected horizontally across the light pipe by a trapezoidal slope composed of side walls 49a and 49b.

  FIG. 6A also shows an input port 47 that can accommodate another light source. However, in some cases, only one light source is used at one end of the light pipe core 42, such as at the input port 45. If such a configuration is used, the input port 47 should be replaced with a reflective material to enhance the internal light reflective properties of the subassembly.

  FIG. 6B shows the dimensions of one implementation of a light pipe core 42 suitable for use with a bill validator. A suitable light pipe core has a bottom length BL of about 97.92 mm, a width W of about 12.5 mm, and a height H of about 5.38 mm. The top length TL is about 77.49 mm and is located approximately in the center above the bottom length so that the slope of the first end portion 58 and the slope of the second end portion 59 are substantially the same. . The slope of these portions may coincide with the first angled wall 49a and the second angled wall 49b formed by the first and second reflective shell portions 46,48. The top surface 44 of the light pipe core 42 can include a diffuser surface 43 for controlling the light intensity output. FIG. 6C shows an enlarged view of portion C of FIG. 6B in which the array of protrusions 41 is arranged in a pattern on the upper surface 44. The pitch of the protrusions can be adjusted so as to balance the intensity of light emerging along and across the light bar so that the light distribution is substantially uniform. In one implementation, the density of the protrusions increases as the diffuser area is further away from the LED light source. In this way, a local spot area is formed where the TIR condition is broken and light can exit the core. In some implementations, the protrusions are generally cylindrical in shape, although other shapes are possible.

  FIG. 7 is an enlarged simplified side schematic diagram 70 illustrating a suitable BEF prism structure 72 manufactured by Minnesota Mining and Manufacturing Corporation (“3M Company”) manufactured by the same company. Each prism structure 72 has a top 74 that is generally parallel to the adjacent top. As shown, about 50% of the light from the light source is reflected back by the BEF and reused, increasing the usable refracted light by 40% to 70%.

  FIG. 8A is an enlarged simplified exploded perspective schematic view of an alternative implementation of an optical core assembly 80 for a document identifier. One suitable configuration of the components includes a rectangular light pipe core 82, BEF 50, and LCC 52 that can include an upper diffusing surface to provide light into the document identifier. The BEF 50 has each apex 74 of the prism structure 72 approximately parallel to the open wall 78 of the LCC, and approximately parallel to the longitudinal “L” edge of the light pipe core 82 and to the short side “S” of the core. Aligned to be vertical. A suitable BEF available from 3M Company is BEF90 / 50, where 90 is the prism angle and 50 is the prism pitch in micrometers (μm). A suitable LCC 52 can be configured to control the geometry of the distribution of light exiting the LCC 52, as described above.

  FIG. 8B shows an alternative implementation of the optical core assembly 200 that has the same dimensions as FIG. 8A and may be suitable for use with a document identifier. The optical core assembly 200 can be a unitary structure, controlling the optical core 202, the prism structure layer 204 for increasing the intensity of the output light, and its direction as the light exits the assembly in the Z direction. LCC 206 (similar to LCC 52) can be included. A light diffusion layer (not shown) may also be included. For some applications, embodiments including more or fewer layers may be utilized. For example, embodiments including optical core 202, diffusion layer, and LCC 206 may be suitable for use in document identification applications.

  FIG. 9 is a simplified diagram of another implementation of a light pipe core 84 that can be implemented as described above with reference to FIGS. 8A and 8B. In this implementation, the LEDs are arranged vertically and the light pipe core is a simple rectangular parallel pipe as shown. In one application, six wavelengths are used and a single LED package accommodates two or three dies. Depending on the wavelength, four dies can be used, two at each end of the light pipe. FIG. 10A is a geometric mapping of dies in a package per wavelength when four dies are used, and FIGS. 10B and 10C are when only two dies are used. In one suitable configuration, each LED package can include a white reflective housing or package to optimize light output, and openings 45 and 47 (see FIG. 4A) accommodate this package. And of minimal size to limit any optical loss in inefficient coupling. The inner surface of the light housing for each LED light source can include a reflective material, which can be a diffuse reflective material. A suitable LED package is the OSRAM Company's TOPLED ™ series. The LED package can be made of a plastic material similar to the reflective shell. For example, the light housing can be formed of a white material to allow a substantially flat spectral response to occur at least from the visible wavelength to the near infrared wavelength spectral region. Light is extracted from the light pipe core 84 by a diffuser structure, which is formed by sanding the surface or by forming a shaped rough random structure on the top surface of the light pipe core. can do. Alternatively, as described above with reference to FIG. 6C, the protrusion array can be formed on the upper surface so as to function as a diffuser. In addition, other diffuser structures can be used.

  Thus, various implementations of document identifier subassemblies have been disclosed. Those skilled in the art will appreciate that various additions and modifications can be made. For example, one alternative configuration includes a second set of BEF and LCC (or prism layer and louver layer) whose optical structure is 90 ° from the first set to control the distribution of light in the elongated direction of the light bar. Set to Other implementations are within the scope of the claims.

Claims (18)

In a subassembly for a document identifier,
A housing;
A light pipe core having an upper diffusing surface and installed in the housing;
A light control component associated with the upper diffusing surface and including at least one aperture;
A subassembly comprising a plurality of light emitting diodes (LEDs) coupled to the housing, wherein at least one LED includes a plurality of LEDs having different wavelengths from another LED.   The subassembly of claim 1, wherein the light control component is formed of a polymeric material.   The subassembly according to claim 1 or 2, wherein the light control component comprises an aperture array.   The subassembly according to any one of claims 1 to 3, wherein each opening has an elongated shape.   The subassembly according to claim 1, further comprising a prism structure layer between the upper diffusion surface and the light control component.   The subassembly according to claim 5, wherein the prism structure is a brightness enhancement film.   The subassembly according to any one of claims 1 to 6, wherein the diffusing surface comprises at least one of a random structure, a constant pitch pattern structure, or a variable pattern of protrusions.   The subassembly according to any one of the preceding claims, wherein the housing includes at least one input light port at at least one end of the light pipe core.   A subassembly according to any preceding claim, wherein the housing includes a reflective inner surface. In a light control component for controlling the geometric distribution of light from a lighting source,
A light control component comprising at least one opening open to the light control component, the light control component configured to limit an exit angle of light transmitted through the at least one opening.   The light control component of claim 10, wherein the at least one aperture is further configured to limit the light exit angle differently in two orthogonal directions.   The light control component of claim 10, wherein the at least one aperture is configured to limit a light exit angle approximately equally in all directions.   The light control component of claim 10, wherein the at least one opening extends substantially the entire length of the light control component.   The light control component of claim 10, wherein the at least one opening segments the light control component lengthwise.   15. A light control component according to claim 10 or claim 14, wherein the at least one opening segments the light control component in a width direction.   The light control component of claim 10, comprising a plurality of apertures.   The light control component of claim 16, comprising at least one bridge between adjacent openings.   The light control component is opposite to at least one detector capable of receiving light traveling through the light control component, the detector having at least one bridge in the field of view of the detector; The light control component of claim 17, arranged to be outside.

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